The Metallic model

The metallic model describes the structure of metals. Metals are made up of an of array of positive metallic ions in a sea of mobile electrons. The word array means an orderly arrangement. eg. An array of soldiers lining up in a parade.

The valence or outer electrons of metals are delocalized. Delocalized means that the electrons are not bound to one particular atom. ie. They are 'not local'. The valence electrons are constantly moving from atom to atom. Refer to the image of the metallic model.

The electrostatic attraction between the positive metallic ions and the delocalized electrons is called a metallic bond.

Questions

1. Describe the metallic model? Metals consist of .....

2. The valance electrons of metals are delocalized. What does 'delocalized' mean?

3. What is a metallic bond?

Further explanation

The valence or outer electrons move from one atom to another, like the game 'pass the parcel'. As they move they create positive ions. The positive ions have the same electron configuration as a noble gas. This is how metals achieve a stable electron configuration.

The electron configuration of sodium is 2.8.1. Sodium has 3 energy levels with 2 electrons in the first shell, 8 in the second shell and 1 electron in the third shell. A stable octet (2.8) arrangement is achieved as the valence electron moves from one sodium atom to another. Positive metallic ions (2.8) are produced in the process.

Question

4. How do metallic atoms achieve a stable arrangement of electrons?

The metallic bond is multi-directional in nature as the valence electrons are constantly moving.

This is why metals can be bent and beaten into various shapes without shattering like glass. The metallic bond is like a Rubik's cube. The multi-directional nature of the bond allows metals to bend in various directions without breaking. Eventually however, stress in the metal lattice causes it to break.

Question

5. Why can metals be bent in various directions?

Student Metallic Model

In the following image the raspberry jubes represent the positive metallic ions and the sour strips show the movement of the valence electrons.

In this metallic model there is an orderly arrangement or array of raspberry jubes in a sea of sour strips!

Properties of metals

Metals

are good electrical conductors

are good conductors of heat.

are malleable* and ductile.**

have lustre (also spelt luster) or shine.

have variable melting points.

Explanation of metallic properties

The metallic model can help explain the properties of metals.

Properties of metals

Explanation of the properties of metals

Good electrical conductors

The valence electrons are mobile and are easily moved in an electric field.

Good conductors of heat

Heating causes the kinetic energy of particles to increase. Mobile electrons travel quickly throughout the metal and transfer their kinetic energy to atoms.

Malleable* and ductile**

The metallic bond is the attraction between the positive metallic ions and the mobile electrons. Since these electrons are constantly moving the metallic bond is multi-directional in nature. The bond is similar to a Rubik's cube which can be turned in many directions.

Lustrous or shiny

The valence electrons are constantly moving. Visible light is reflected by these mobile electrons in various directions. This produces 'lustre' or 'shine'. Note: Due to oxidation reactions the metal surface may have to be cleaned to reveal the 'shine. eg. Cleaning the surface of lead foil with steel wool.

Variable metal points

Metals have variable melting points due to differences in the strength of the metallic bonds. Mercury melts at -39°C (-38 °F) and has a weak metallic bond. Tungsten melts at 3410°C (6170 °F) and has a strong metallic bond.

*Malleable means being able to be beaten into a shape. A panel beater makes a living by beating car panels back into shape.

**Ductile means being able to be drawn out into a wire.

Questions

6. Why are metals good conductors of electricity?

7. Why are metals good conductors of heat?

8. What do the words 'malleable' and 'ductile' mean?

9. Why do metals have lustre?

10. Some metals like mercury melt at low temperatures. Some metals like tungsten have very high melting points. Explain why?